Background: This study was designed to investigate the prognostic value of the lymphocyte to monocyte ratio (LMR) in patients with gallbladder carcinoma (GBC). Patients and Methods: We retrospectively enrolled 154 consecutive GBC patients from 2005 to 2017 in this study. The LMR of preoperative blood samples was calculated by dividing the lymphocyte count by the monocyte count. A receiver operating characteristic (ROC) curve was employed to identify the optimal cut-off value of the LMR in the determination of overall survival (OS). The Kaplan-Meier method was utilized to assess OS, and the Log rank test was employed to compare survival differences. Univariate and multivariate Cox regression analyses were conducted to detect independent prognostic indicators. Results: The optimal cut-off point for the LMR was 4.76 according to the ROC curve. Patients <= 60 years old with an LMR <4.76 experienced significantly worse OS than those with an LMR >4.76 (hazard ratio (HR): 0.399, 95% confidence interval (CI): 0.265-0.602, P<0.001); however, the prognostic value of the LMR was not determined in patients >60 years old or among the entire study cohort (both P>0.05). Significantly poorer OS was observed in patients >60 years with an LMR <= 4.21 compared to those with an LMR >4.21 (HR: 1.830, 95% CI: 1.129-2.967, P=0.014). Multivariate Cox regression analysis indicated that both the high and low LMR cut-off values were independent risk factors for OS (HR: 0.272, 95% CI: 0.105-0.704, P=0.007; HR: 0.544, 95% CI: 0.330-0.895, P=0.017). Conclusion: The LMR is an independent prognostic indicator for GBC patients, the cut-off value of which is age dependent.